BITS 0.2
( ( object-id )*, label?, ( caption )?, ( alt-text | long-desc | email | ext-link
| uri )*, ( disp-quote | speech | statement | verse-group | def-list | list | alternatives
| chem-struct-wrap | graphic | media | preformat | table )*, ( table-wrap-foot | attrib
| permissions )* )
BITS 1.0
( ( object-id )*, label?, ( caption )?, ( abstract )*, ( kwd-group )*, ( alt-text
| long-desc | email | ext-link | uri )*, ( disp-quote | speech | statement | verse-group
| def-list | list | alternatives | chem-struct-wrap | code | graphic | media | preformat
| table )*, ( table-wrap-foot | attrib | permissions )* )
BITS 2.0
( ( object-id )*, label?, ( caption )?, ( contrib-group )*, ( abstract )*, ( kwd-group
)*, ( alt-text | long-desc | email | ext-link | uri )*, ( disp-quote | speech | statement
| verse-group | def-list | list | alternatives | chem-struct-wrap | code | graphic
| media | preformat | table )*, ( table-wrap-foot | attrib | permissions )* )
BITS 2.1
( ( object-id )*, label?, ( caption )?, ( legend )*, ( contrib-group )*, ( abstract
)*, ( kwd-group )*, ( subj-group )*, ( alt-text | long-desc | email | ext-link | uri
)*, ( disp-quote | speech | statement | verse-group | def-list | list | alternatives
| chem-struct-wrap | code | disp-formula | graphic | media | preformat | table | xref
)*, ( table-wrap-foot | attrib | permissions )* )